Welcome to this lesson from the Oak National Academy.

Today's lesson is about explaining the effect of temperature on the rate of cellular respiration, and it's taken from the unit, aerobic and anaerobic cellular respiration.

Hiya, I'm Mrs. Wheate, and I'm gonna be your teacher for today's lesson.

By the end of today's lesson, you'll be able to analyse data collected from a respirometer, calculate the rate of cellular respiration, and explain the effect of temperature on the rate.

Let's have a look at our keywords.

Today's lesson has got five keywords, and I'll read them out now.

Rate, a measure of how much change occurs per unit of time.

Cellular respiration, an exothermic chemical process that transfers energy for life processes using glucose as a fuel.

Respirometer, apparatus used to measure the rate of respiration in small organisms. Enzyme, a biological catalyst.

Denature, when bonds in an enzyme molecule break and the molecule changes shape.

So if you wanna read those through again, I'll be quiet for five seconds, but if that's not enough time, you can pause the video and then click play when you're ready to come back to the lesson.

Today's lesson is in two parts.

In the first part of the lesson, we're gonna analyse the data that you can collect when you use a respirometer to investigate the rate of respiration.

And then after that, we will explain the effect of temperature on respiration.

But first, let's look at data analysis and the rate of respiration.

The rate of aerobic cellular respiration in small organisms, such as germinating peas, can be measured using a simple respirometer, and that's what this equipment in the diagram is.

As the peas respire aerobically, they use oxygen from the air in the boiling tube, and this causes the coloured liquid to move towards the boiling tube where the germinating peas are.

Measuring the distance the liquid travels enables us to calculate the rate of respiration.

So the distance the liquid travels is not in of itself the rate of respiration, but it allows us to calculate it.

I'll explain what I mean by that.

So rate is a measure of how much change occurs per unit of time.

So in this experiment, we calculate the rate of respiration using the distance that the coloured liquid moved in five minutes.

That's how long the peas were left to do their thing.

So in this experiment, the unit for rate is millimetres per minute, because we calculate the rate by getting the distance they travelled in millimetres divided by the time they're allowed to respire, five minutes.

So if we look at that in the table, we can see that these peas were exposed to two temperatures, 25 degrees and 35 degrees Celsius.

When the peas were exposed to 25 degrees Celsius, they moved seven millimetres.

When they're exposed to 35 degrees Celsius, they moved 12 millimetres.

So how do we turn that into a rate? So for 25 degrees Celsius, we're gonna do seven, which is the distance they travelled, divided by five.

And that give us 1.

4, and that is our rate of respiration.

Let's do it again at 35 degrees Celsius.

So the distance they travelled, the distance the coloured liquid travelled was 12 millimetres.

So we're doing 12 to run it by five, and that gives us 2.

4.

So that's how we use the distance that the coloured liquid travelled in order to get us to the rate of respiration.

Okay, we're gonna check to see if you understood that now.

Calculate the rate of respiration for each temperature.

A reminder that in this experiment, the peas will have to respire for five minutes.

I'll give you five seconds to calculate your answers, but if you want a bit more time, you can click pause and then click play when you're ready to move on with the lesson.

Let's have a look at your answers.

So for 25 degrees Celsius, you should have done 8.

5 divided by five because the peas were left to respire for five minutes, and that equals 1.

7.

20 degree Celsius, 11 divided by 5, 2.

2.

And then for 35 degrees Celsius, 13 divided by 5, 2.

6.

Great job if you got that right.

We can use the data from the experiment to compare the rate of respiration at different temperatures.

Our comparison points out similarities and differences, and it does this by using words such as more or less, or using words that end in ER, such as bigger, or EST, such as biggest.

So using the data in the table below, I want you to compare the rate of respiration at different temperatures and try and think about the words you're gonna use.

Perhaps words such as more or less, or words that end in ER, EST, so just to ensure that it's a comparison.

I'll give you five seconds now to think about that, but if that's not enough time for you, click pause and click play when you're ready to move on with the lesson.

Okay, let's have a look at the kind of thing you could have written.

So my example is, the table shows that the rate of respiration is greater at the highest temperatures than it is at the lower temperatures.

Hopefully, you got something like that too.

Let's keep practising that.

Whose statement best compares the rate of respiration at different temperatures? Is it Izzy? The rate of respiration changes depending on the temperature.

Or Jun, the rate of respiration is greater at higher temperatures than it is at lower temperatures.

Or is it Alex? When temperature is low, the rate of respiration is low.

Take five seconds, or if you want some more time to think about it, click pause and click play when you're ready to see the answers.

Okay, so the statement that best compares the rate of respiration at different temperatures is Jun's.

We're gonna have a look at all the statements to help us figure out why Jun's is the best.

We'll start with Izzy's first.

The rate of respiration changes depending on the temperature.

This is a true statement.

It's correct, but it's incredibly vague.

It doesn't really tell us anything really about respiration and about temperature.

It doesn't describe the relationship between them at all, and it definitely doesn't compare what the rate of respiration is like at a high temperature compared to what it's like at a low temperature.

Let's have a look at Alex's statement.

When temperature is low, the rate of respiration is low.

This is a more detailed statement, but it's still not a comparison.

For example, it's not using words that end in ER or EST to help make the point.

Let's look at Jun's.

The rate of respiration is greater at higher temperatures than it is at lower temperatures.

You don't need to use a word that ends in ER, but it really does help make the point that you are comparing.

Well done if you got that right.

When describing data, it's also useful to describe the general trend and then describe a specific example from the data.

For example, you could say, as the temperature decreases, the rate of respiration decreases.

A specific example of that might be the temperature at 45 degrees is half of the rate that it is at 40 degrees.

That's looking at one specific example of two data points in the table and then seeing if there's some kind of relationship between them, maybe halving or doubling or tripling.

Let's look at the data table here on the screen now, though.

So what I want you to do is I want you to describe the relationship between the rate of respiration and the temperature, and I want you to give, describe the general trend first and then give a specific example from the data.

Is something halving, or doubling, or tripling? That kind of thing.

So you can have five seconds to do that, but if you want more time, click pause and click play when you're ready to move on.

Okay, let's have a look at the kinda thing that you could have said.

So the general trend in this would be, as the temperature increases, the rate of respiration increases.

And a specific example is that the rate of respiration at 35 degrees Celsius is double the rate at 20 degrees celsius.

Great job if you noticed that.

Let's keep practising that skill.

Which of the statements about the table is correct? Is it A, as the temperature increases, the rate of respiration increases, B, the rate of respiration at 35 degrees is four times the rate that it is at 15 degrees celsius, C, the rate of respiration at 15 degrees is half the rate at 25 degrees, D, there is no relationship between the rate of respiration and temperature? You can have five seconds, but if that's not enough time for you, click pause and click play when you're ready to see the answers.

Okay, the answer is A, as temperature increases, rate of respiration increases.

B is also correct.

The rate of respiration at 35 degrees is four times the rate at 15 degrees.

Great job if you got those right.

This is the first practise task of today's lesson.

A student used a respirometer to investigate the effect of temperature on the rate of respiration in germinating peas.

They measured the distance the coloured liquid moved for five minutes.

They repeated this three times at each temperature of 15 degrees, 25 degrees and 35 degrees Celsius.

So answer the following questions about the experiment.

Number 1, complete the results table on the worksheet.

Number 2, explain why the units for rate of respiration in this experiment are millimetres per minute.

And number 3, use the table to describe the effect of temperature on the rate of respiration.

You'll need to pause your video now in order to give yourself enough time to do that and click play when you're ready to see the answers.

Good luck.

Okay, let's have a look at the answers.

So at 15 degrees, the answer should have been 5.

0.

Not just 5, it should have been 5.

0 because that's the amount of decimal places that all the other data points are in the table.

So 5.

0, not just 5.

At 25 degrees, the mean should have been 11.

5.

At 35 degrees, the mean should have been 15.

0.

So our rate of respiration column should say 15 degrees should be 1.

0, 25 degrees, 2.

3, and 35 degrees, 3.

0, right.

Question 2, explain why the units for rate of respiration in this experiment are millimetres per minute.

A rate is a measure of how much change occurs per unit of time.

The rate was calculated by measuring the distance of a coloured liquid, the distance a coloured liquid moved, measured in millimetres over five minutes.

Number 3, use a table to describe the effect of temperature on the rate of respiration.

The table shows that the rate of respiration increases as the temperature increases.

The rate of respiration measured at 35 degrees Celsius, Celsius, is three times greater than the rate of respiration at 15 degrees Celsius.

Great job if you got that right.

We've completed the first part of today's lesson.

We've carried out our data analysis about the rate of respiration, and now we're gonna explain the effect of temperature on respiration.

Temperature affects the rate of respiration because cell respiration is controlled by enzymes.

An enzyme is a biological catalyst.

It speeds up the rate of reaction.

Every enzyme has an active site where its substrate fits.

An enzyme's active site is specific for its substrate, like a lock and its key.

So here's our enzyme, and here's our substrate that fits perfectly into the active site, and that's just like how a key fits perfectly into a lock.

Think about the key to your front door.

There might be many copies of that that you and all your family members have, but they're all exactly the same type of key, and they fit into the front door perfectly.

If you tried to open the front door with the key from the back door or a key from a window, it wouldn't fit, and it wouldn't work.

So that's how a substrate, like that's similar to how a substrate fits into the active site of an enzyme.

Okay, let's check to see if you understood that.

Which of the following is a biological catalyst? Is it A, an enzyme, B, a key, C, a lock, or D, a substrate? Take five seconds.

If you want some more thinking time, click pause.

Click play when you're ready to see the answer.

It is A.

Well done if you got that right, but let's take a look at the other answers.

So B and C, key and lock.

Those are incorrect.

Those are incorrect because talking about a lock and a key is a helpful metaphor or a model that helps us to describe an enzyme or substrate, but they aren't the enzyme itself.

Let's look at D, substrate.

Why is that wrong? Well, a substrate is something that fits into an enzyme's active site.

The only thing in this list, which is the biological catalyst, which speeds up chemical reactions, is A, the enzyme.

So we've talked about one enzyme, a substrate, and an active site is.

Now let's talk about the effect of temperature on the rate of respiration.

As temperature increases, the enzyme and substrate molecules move faster as they have more energy.

This means there are more successful collisions of substrate molecules with enzyme active sites, so more reactions happen in every unit of time.

So that means the rate increases.

The increasing temperature also causes the molecules that make up the enzyme to vibrate faster.

As temperature increases above the optimum temperature, the molecules that make up the enzyme continue to vibrate but with more force.

The bonds holding the enzyme molecules together start to break, and the enzyme changes shape.

The enzyme denatures.

The substrate cannot fit into the active site.

As the high temperature denatures the enzyme by breaking chemical bonds, its active site no longer fits the substrate.

Therefore, at temperatures above the optimum, the rate decreases to zero.

Let's do that again, looking at the graph.

So we can see at the beginning of the graph, as temperature increases, the rate of reaction increases.

We get to a point on the graph, which is the optimum temperature for the enzyme to function.

After the optimum temperature, as the temperature increases past the optimum, then the rate of reaction starts to decrease, and this is because the enzyme has been denatured by the high temperatures.

Let's look at that in the context of our experiment.

Here is a table showing the results of the respirometer experiment carried out at equal intervals between 15 and 45 degrees.

I'll give you a few seconds now to read through the table to make sure that you understand it.

If the respirometer experiment were carried out above the optimum temperature, the rate of respiration would decrease eventually to zero.

This is because the enzymes necessary for cellular respiration to occur would denature at temperatures above the optimum.

Let's use what we've learned about analysing data to describe the relationship between the rate of respiration and temperature seen in this table.

Remember to describe the general trend and then any specific patterns that you see.

I'll give you five seconds to have a think about your answer, and then you can get playing when you're ready to continue with the lesson.

How did you do? You could have said something like, as the temperature increases, the rate of respiration increases.

This is until 35 degrees Celsius.

After 35 degrees Celsius, as the temperature increases to 45 degrees, the rate of respiration decreases.

There weren't any specific patterns in this data, such as doubling or halving or tripling.

There isn't always a pattern like this, but it is still good practise to check to see if there is one to comment on.

Okay, now I want you to use what we just said about enzymes to explain the pattern that we see in the data.

Again, you can have five seconds, or if that's not enough time, click pause and click play when you're ready to move on.

How did you do? You could have said something like, as the temperature increases, the enzymes and substrate collide more frequently, which causes an increase in the rate of respiration.

This is until the optimum temperature is reached somewhere between 35 and 45 degrees.

After this temperature, the enzyme begins to denature, and this causes a decrease in the rate of respiration.

True or false? Increasing the temperature allows enzyme reaction rate to keep increasing forever.

Is that true, or is that false? Take five seconds, or if you want some more thinking time, click pause and click play when you're ready to see the answers.

Okay, that is false.

But why is it false? Take another five seconds, or if you want some more time, click pause.

Click play when you're ready to see the answers.

It is false because high temperatures above the optimum cause enzyme molecules to change shape, so the enzyme works less well, and reaction rate drops.

At very high temperatures, the enzyme is denatured and stops working, so the rate equals zero.

Great job if you got that right.

This is the final practise task for today's lesson.

Answer the following questions.

Number 1, define the following key terms, enzyme, active site, and denature.

Number 2, describe what happens to the rate of an enzyme control reaction as temperature increases above the optimum.

You'll need to pause the review now to give yourself enough time to think about your answers and to write 'em down, and click play when you're ready to move on with the lesson.

Let's have a look at the answers to question 1 and 2.

Define the following key terms, enzyme, a biological catalyst, B, active site, the part of an enzyme where it's substrate fits, C, denature, when the bonds in an enzyme are broken, changing its shape.

This leads to the active site no longer fitting with the substrate.

Question 2, describe what happens to the rate of an enzyme control reaction as temperature increases above the optimum.

As temperature increases above the optimum temperature, the molecules that make up the enzyme continue to vibrate with lots of force.

The bonds holding the enzyme molecules together start to break, and the enzyme changes shape.

The enzyme denatures.

The substrate cannot fit into the active sight and the rate of reaction slows and eventually drops to zero.

Great job if you got that right.

Okay, a student used a respirometer to investigate the effect of temperature on the rate of respiration in germinating peas.

They boiled a germinating peas at 100 degrees Celsius for three minutes.

After setting up the respirometer, they measured the distance the coloured liquid had moved after five minutes.

They repeated this three times at 15 degrees, at 25 degrees, and at 35 degrees Celsius.

3a, describe the results you would expect to see.

3b, explain your answer to 3a.

So again, you'll need to pause the video to give yourself enough time to think out these answers, and then click play when you're ready to see the answers.

Good luck.

Let's have a look at the answers.

3a, describe the results you'd expect to see.

There will be very little change in the distance of liquid moved at any of the temperatures.

B, explain your answer to 3a.

I think this is because the student boil the germinating peas at 100 degrees Celsius.

This would've denatured the enzymes necessary for cellular respiration.

Therefore, the peas would not be using oxygen from the air for aerobic cell respiration, so the coloured liquid would not be drawn closer to the organism.

Any changes in the distance of the coloured liquid would be due to other factors, such as changes in atmospheric pressure.

Amazing work.

Well done if you got that right.

Well done today on all your hard work, and now let's summarise what we've learned to help it stay in our memories.

The rate of cellular respiration in small organisms can be measured using a simple respirometer.

As the organisms respire aerobically, they use oxygen from the air in the respirometer apparatus, which causes a coloured liquid to move.

The rate of respiration is calculated by measuring the distance the liquid travel in millimetres and dividing this by the period of time the experiment lasted in minutes.

The units of rate are millimetres per minute.

Temperature increases the rate of respiration up to an optimum because there are more collisions of substrate molecules with enzyme active sites.

Increasing the temperature above the optimum causes the enzyme molecules to denature, change shape, so the rate of reaction drops.

I hope you enjoyed today's lesson, and I hope to see you again soon for our next lesson.